As mobile device technology continues to develop and demand therefor continues to increase, demand for secondary batteries as energy sources is rapidly increasing. Among these secondary batteries, lithium secondary batteries, which exhibit high energy density and voltage, long cycle lifespan, and low self-discharge rate, are commercially available and widely used.
In general, secondary batteries have a structure in which an electrode assembly including a cathode, an anode, and a separator disposed therebetween is accommodated in a stacked or wound form in a battery case made of a metal can or a laminate sheet and an electrolyte is injected thereinto or the electrode assembly is impregnated with an electrolyte.
Among these secondary batteries, in a pouch-type secondary battery consisting of a high-voltage battery cell, one of the main research tasks is to prevent deterioration of battery performance due to generation of gas when a battery is subjected to activation and in use. For example, when a secondary battery is activated, a large amount of gas is generated, which increases the volume of the battery or damages a sealing portion of a battery case and, consequently, the generated gas leaks outside. Thus, an electrolyte leaks via the damaged sealing portion and, accordingly, battery performance is deteriorated.
In addition, even when gas is generated by decomposition of an electrolyte at an electrode due to abnormal battery operating conditions such as an overcharge state in which current and voltage when a battery is in use are higher than allowable current and voltage, exposure to high temperature, and the like, batteries are damaged due to the reason described above.
In addition, in secondary batteries, an electrolyte may be depleted due to leakage thereof due to damage to a sealing portion of a battery case, oxidation thereof, or the like and, accordingly, battery lifespan is dramatically reduced.
In addition, when conventional pouch-type batteries are manufactured, excess electrolyte is injected to guard against depletion of an electrolyte and thus a skin-tight structure of a pouch-type battery is not maintained and resistance is increased due to separation of an interface between stack cells, which results in reduction in battery lifespan.
Therefore, there is an urgent need to develop a novel battery cell that addresses the problems described above.